New animation feature

When animating a function by varying a constant, the animation could keep the function for every increment. A clearer explanation can be given with an example. In optics one often wants to illustrate the image that several light beams would form. If I have the equation for a light beam at a given angle, I can insert that equation/function with many different angles to form the image I want, but, to avoid having dozens of functions, the animation feature provided above could solve that.